[Cancer of the endometrium caused by antiestrogens]

Tamoxifen is the most widely used non-steroidal antiestrogen compound for adjuvant treatment of postmenopausal breast cancer. Tamoxifen has both antiestrogen and estrogen-agonistic activity, which depends on the target tissue involved owing its systemic distribution. Upon the endometrium the agonistic estrogenic effect, so-called "paradoxical" effect, is suggested to induce proliferative changes such as hyperplasia or carcinoma. The authors report four cases of endometrial cancer developed in postmenopausal patients with breast cancer receiving tamoxifen. According to the literature data, the relationship of the tamoxifen to the endometrial remains uncertain: women with breast cancer are at increased risk for this neoplasm sharing common aetiologic hormonal factors and, in most published case reports, the uterine cavity has not been checked up before starting tamoxifen administration.